Lidocaine Infusions for Chronic Pain in Children

Reports have shown that intravenous lidocaine infusions have been effective in relieving chronic pain that has been resistant to other therapies, with minimal side effects. The investigators would like to determine whether severity of pain and degree of chronic-pain related disability could be reduced with lidocaine infusion in children and to understand whether the dose of lidocaine correlates with blood levels in the same manner as it does in adults. The investigators will recruit 24 patients aged 8-18 with chronic pain that has not been relieved by standard therapies. Each patient will receive a lidocaine infusion over 2 hours. Blood will be drawn for lidocaine concentration before the beginning of the infusion, immediately after and 0.5, 2 and 4 hours after. Severity of pain and degree of disability will be recorded using a questionnaire measuring pain scores, sleep disruption, social disruption, physical abilities and school attendance before the infusion, weekly for 2 weeks and then 4 weeks after. This study will help the investigators better understand the effectiveness and safety of intravenous lidocaine for chronic pain in children.

Inclusion criteria

• Diagnosed with a chronic pain condition (> 3 months) other conventional medical therapies (anticonvulsants, tricyclics etc), have not been effective.
• American Society of Anesthesiologists class 1 or 2
• Age 8-18 years
• Ability to understand and use the numeric rating scale to rate their pain and to understand and answer other questionnaires
• Negative pregnancy test in participants of child-bearing potential (Females 12 years of age and older, or menarchal if under 12)

Exclusion criteria

• History of seizures
• Known liver or renal disease
• Patient taking strong CYP1A2 inducers or inhibitors (fluvoxamine, phenytoin, cimetidine, amiodarone) or beta blockers (propranolol, metoprolol, nadolol)
• Allergy or sensitivity to lidocaine or other local anesthetic
• Cardiac conduction anomalies (eg. Heart block, Wolff-Parkinson-White)
• Serum electrolytes (potassium, sodium, magnesium or calcium) outside of reference ranges
• Pregnancy

Withdrawal Criteria

• Patient or parent/guardian request
• Refusal to have intravenous access and serum levels drawn
• Inability to complete pain scores on the questionnaires (paper or electronic) at the first infusion and weekly for 2 weeks and at one month following infusion
• Baseline free carnitine concentration < 26 micromoles/L or total carnitine < 32 micromoles/L (reference values from SickKids Department of Pediatric Laboratory Medicine "Guide to Laboratory Services")